Text normalization (TN) converts text from the canonical written to the spoken form, and it is an essential pre-processing step of text-to-speech (TTS) systems, see Figure REF .
Sentences consist of plain and special words or phrases, also known as semiotic tokens [1]}. Semiotic tokens can be grouped into classes like cardinals, fractions, or dates. Semiotic tokens require non-trivial normalization while plain words remain the same. In the example shown in Figure REF  “1/4" is the only semiotic token and thus needs to be normalized.
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